Balanced radiator system

ABSTRACT

A transmission line system for having a primarily signalinitiating section and a primarily signal-radiating section, along both of which line sections traveling electromagnetic waves may propagate without adverse interference of impedance discontinuities, is employed cyclically as an energy storage device and as an impulse radiating device having spatially directive characteristics.

United States Patent Ross et al.

BALANCED RADIATOR SYSTEM Gerald F. Ross, Lexington; David Lamensdorf,Cambridge, both of Mass.

Assignee: Sperry Rand Corporation Filed: June 15, 1970 Appl. No.: 46,079

Inventors:

US. Cl ..325/l05, 307/246, 325/125, 325/129, 325/152, 325/164, 325/166,325/179, 330/20, 343/701 Int. Cl. ..H04b 1/04 Field of Search ..325/101,102, 106,107,120, 325/121,l25,129,160,164,166,167, 169,178, 179,185-187,105; 328/66-68; 333/13, 152, 4,19, 20, 32; 343/701; 307/246 PULSEGENERATOR Z 1 OHMS L HORN ANTENNA 51 Apr. 25, 1972 [56] References CitedUNITED STATES PATENTS 2,422,176 6/1947 Benioff ..325/l06 3,405,28710/1968 Miller 3,317,839 5/1967 Landecker ..328/l06 PrimaryExaminerRobert L. Griffin Assistant Examiner-Albert J Mayer Attorney-S.C. Yeaton ABSTRACT A transmission line system for having a primarilysignal-initiating section and a primarily signal-radiating section,along both of which line sections traveling electromagnetic waves maypropagate without adverse interference of impedance discontinuities, isemployed cyclically as an energy storage device and as an impulseradiating device having spatially directive characteristics,

13 Claims, 18 Drawing Figures Patented A ril 25, 1972 3,659,203

4 Sheets-Sheet l FIG.2. FIG.3.

PULSE GENERATOR Z r OHMS HORN ANTENNA INVENTORS GERALD F.- R055 0/! V/DLA'ME/VSDORF ATTUR/VEY Patented April 25, 1972 3,659,203

'4 Sheets-Shoot '0' ATTORNEY Patented A ril 25, 1972 3,659,2034.SheotB-Sheet 4 S SWITCH STATE ERADIATED "14-140 0? 'I/VVE/VTORS GERALDF. 17055 DAV/D LAME/VSDORF ATTORNEY BACKGROUND OF THE INVENTION systemboth for signal generation and for signal radiation into space.

2. Description Of The Prior Art Known prior art antennas are not readilyadaptable to the radiation or reception of sharply pulsed or steppedelectromagnetic signals, even though capable of relatively broad LIIband transmission of ordinary continuous wave signals. For

example, the log-periodic array, the log-spiral antenna, and many of theknown guided or surface wave antenna structures lack suitable propertiesfor the purpose, since they present dispersive impedance discontinuitiesand because propagation of wave energy on or within the antennastructure is characterized by dispersive TE, TM, or other suchpropagation modes. Thus, the phase characteristic of the response ofsuch antennas is not linear.

Many prior directive antennas operating in high frequency ranges haveused excitation systems coupling energy tobe transmitted to theradiating structure by unbalanced transmission lines. Such couplingarrangements are sometimes selected because of the relatively large sizeof hollow wave guides in certain frequency ranges, or because of otherknown considerations, including band width requirements.

However, where antennas are to be achieved yielding distortionlesstransmission of transient or very short pulse radiations, a designrequirement is that balanced currents flow equally on either side of thedriving point or the effective load of the antenna. If unbalancedcurrents are also permitted to flow, they decrease the efficiency of thetransmitting antenna since they flow in effect to spurious loads inparallel with the desired antenna radiating load. In addition, suchunbalanced currents are well known to produce time domain distortion inthe field pattern of the antenna.

Baluns of various degrees of complexity are often used in the interfacebetween unbalanced transmission lines and balanced antenna radiators,but known designs do not meet band width requirements, produce severedistortions, and often do not representuseful transitions at evenmoderate power levels. Many forms of such baluns do not fully preventgeneration of undesirable unbalanced current fiow.

Furthermore, most known antenna and associated transmitter concepts donot adapt themselves to combinations in such a manner that stepped,transient, or sharp impulse radiations are efficiently generated in acompact, inexpensive structure. In the prior art, the structure andfunction of the transmitter are generally fully separate from thestructure and function of the antenna. Balanced transmitter-antennaconfigurations in which the two substantial parts of the system fullycooperate in determining the nature of the radiated signal are notpossible to achieve by employing known. design techniques.

SUMMARY OF THE INVENTION The present invention relates to an improvedtransmitter antenna configuration employing an electrically smooth,constant impedance transmission line system for propagating TEM modewaves. The transmission line system is employed cyclically for thecooperative storage of energy on the transmission line and for itsrelease by propagation along the transmission line for radiation at theend of a section of the transmission line formed as a flared directiveantenna. Thus, cooperative use is made of the transmission line systemboth for signal generation by cyclically charging the transmission lineat a first rate of charging and for signal radiation into space bydischarge of the line in a much shorter time than for charging.Discharge of the transmission line causes a voltage wave to traveltoward the open end or radiating aperture of the structure. The processoperates to produce, by differentiation, an impulse that is radiatedinto space.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anembodiment of the antenna used in the present invention.

FIGS. 2 and 3 are respectively top and side views of the antenna of FIG.1 and are useful in explaining its properties.

FIG. 4 is a schematic side view of the antenna of FIG. 1 showing circuitelements for exciting the antenna.

FIGS. 5a to 8b are graphs for explaining the operation of the embodimentof F IG. 4.

FIG. 9 is a circuit arrangement alternative to that of FIG. 4.

FIG. 10 is an improved embodiment of the circuit of FIGS. 4 and 9.

FIGS. 11, 12, and 13 are graphs used in explaining the operation of theembodiments of FIG. 10.

FIG. 14 is an embodiment of the invention whose operation isself-synchronized.

' na useful in the present invention. -A suitable antenna for thepurpose has a wide instantaneous band width, so that it may radiate asharp pulse or stepped signal with low distortion of the signalenvelope. Further, a suitable antenna for use in the invention has anenergy focusing characteristic such that energy radiated in apredetermined direction is maximum.

The modified horn antenna of FIGS. 1, 2, and 3 is a preferred form of anantenna having such desired characteristics. As will be seen in FIG. 1,the antenna 3 comprises a structure having mirror image symmetry about amedian plane at right angles to the direction of the vector of theelectric field propagating within the antenna. The same is true of thetransmission line 1, which comprises parallel plate or slab transmissionline conductors 4 and 4a of similar shape. Conductors 4 and 4a arespaced planar conductors constructed of a material capable. ofconducting high frequency currents with substantially no ohmic loss.Further, conductors 4 and 4a are so constructed and arranged as tosupport TEM mode propagation of high frequency energy, with the majorportion of the electric field lying between conductors 4 and 4a and withthe field substantially perpendicular to the major interior surfacesthereof. It will be understoodby thoseskilled in the art that the termTEM mode of wave propagation is that commonly used in the high frequencyliterature to specify a conventional mode of electromagnetic energypropagation. In the TEM or transverse electromagnetic ,mode, both theelectric and magnetic field components of the wave are everywheretransverse to the direction of wave propagation. This is in contrast tothe character of certain other types of conventional electromagneticwaves, such as the transverse electric (TE) and transverse magnetic (TM)wavesQThe TE and TM modes are dispersive modes, while the TEM modeemployed in the present invention is desirably non-dispersive.

The TEM modified horn antenna 3 consists of a pair flared,

flat, electrically conducting planar members 2 and 2a. Members 2 and 2aare generally triangular in shape, member 2 being bounded by flarededges 6 and 6a and an aperture edge 8. Similarly, member 2a is boundedby flaring edges 7 and 7a and an aperture edge 80. Edges 8 and 8a may bestraight or arcuate as shown at 18 and 18a of FIGS. 2 and 3. Eachtriangular member 2 and 2a is slightly truncated at its apex, the trimcation being so constructed and arranged that conductor 4 is smoothlyjoined without overlap at junction 9 to antenna member 2. Likewise,conductor 4a is smoothly joined without overlap at junction 9a toantenna member 2:1. It is to be understood that the respective junctions9 and 9a are formed using conventionally available techniques forminimizing any impedance discontinuity corresponding to the junctions 9and 9a.

It is also to be understood that the flared members 2 and 2a of antenna3 are constructed of material highly conductive to high frequencycurrents. It is further to be understood that the interior volume ofantenna 3 may be filled with an air-foamed dielectric materialexhibiting low loss in the presence of high frequency fields.Transmission line 1 may be similarly filled with dielectric material,such material acting to support conductor 4 in fixed relation toconductor 4a and, likewise, the flared member 2 relative to member 2a.Alternatively, the conductive elements of transmission line 1 andantenna 3 may be fixed in spaced relation by dielectric spacers such asrepresented by spacers l and a seen located adjacent the aperture edges8 and 8a of antenna 3.

The form of the transmission line-l and the antenna 3 as illustrated inFIG. 1 is preferredgin part, because TEM mode propagation therein isreadily established. The TEM propagation mode ispreferred, since it isthe substantially non-dispersive propagation mode and its use thereforeminimizes distortion of the propagating signal. The simple, balancedtransmission line structure permits construction of the invention withminimum impedance discontinuities.

Furthermore, it is a property of the symmetric type of transmission line1 that its characteristic impedance is a function of b/h as defined inFIGS. 1 and 2, where it is seen that b is the width dimension of theconductor major surfaces and h is the distance between the inner facesof the conductors. For example, the ratio b/h is kept constant in theinstance of transmission line 1 because both b and h are constant.

According'to the invention, the antenna 3 is made compatible withtransmission line 1 by using the same value of the ratio b/h for bothelements. In other words, if b/h is kept constant along the direction ofpropagation in antenna 3, the characteristic impedance of antenna 3 willbe constant along its length Land may readily be made equal to that ofline 1. By maintaining a continuously constant characteristic impedancealong the structure including line 1 and antenna 3, frequencysensitivereflections are prevented therein. It has been elected,

for the sake of simplicity of explanation, to show in FIGS. 1, 2, and 3triangular flaring and planar configurations for elements 2 and 20. Itshould be evident, however, that other configurations may readily berealized which maintain a constant characteristic impedance accordingtothe above rule, and that such configurations may also be used withinthe scope of the present invention. The length Lof the flared members 2and 2a must be large relative to the width of the antenna driving pulse(or to the rise time of a stepped driving excitation) or the antenna maylose directivity in azimuth'angle I ."As previously'noted, a system forexciting the inventive antenna of FIGS. 1,2, and 3 should havecompatible properties, such as being balanced in nature and avoiding thecomplicating deficiencies of an interface balun or other similartransition element. The system of FIG. 4 achieves such objectives and,in addition,makes beneficial use of the balanced dual elementconfiguration of antenna 3 as part of the charging line for theexcitation generator. It will beunderstood that certain libertieshavebeen taken in the drawing of FIG. 4 better to explain the structure andoperation of the device disclosed therein. For example, it is seen thatFIG. 4 is intended schematically to indicate antenna conductor elements2 and 2a of FIG..1 as respe'ctive'single wire transmission lines 12 and12a having the same effective electrical characteristics as elements 2and 2a of FIG. .1 and the same radiating characteristics. As a furtherexample, junctions 9 and 9a in FIG. 1 are represented by junctions l9and-19a in FIG. 4. The symbols 4 and 4a in FIG. 1 are represented inFIG. 4 by symbols l4 and 14a and identify the opposed conductors oftransmission line 1. Dimensions in FIG. 4 are grossly exaggerated, suchas the spacing h between conductors 14 and 14a of line 1, as a matter ofconvenience.

At the left end of line 1, conductors 14 and 14a are joined by a seriescircuit comprising battery 21 coupled between resistors 20 and 20a eachhaving a resistance value of R/2 ohms. At the end of line 1 adjacentjunctions l9 and 19a, the conductors 14 and 140 are joined by a seriescircuit comprising an electrically actuatable .switch 23; the bladeterminal 27 of switch 23 is coupled by resistor 22a to conductor 14a,while the contact 26 of the switch is connected through resistor 22 toconductor 14. Resistors 22 and 22a each have a resistance value r/2ohms, where r is equal to the characteristic impedance of line 1 (orantenna 3) in ohms.

Square wave pulse generator 24 which produces the balanced square pulsewave form 24a, is provided for actuation of switch 23. Switch 23 maytake the form of a single pole single throw mercury-wettedreed switch,several varieties of which are readily available on the market. Suchreed switches may be closed and opened according to the presence orabsence of a static magnetic field in the vicinity of the switchcapsule. Thus, pulse generator 24 is adapted to open and close switch 23by the agency represented by dotted line 25, which may be a magneticfield excited by a solenoid (not shown) by pulse wave 240. It will beunderstood that square wave generator 24 may be replaced by a generatorof pulse width modulated waves carrying an intelligence modulation suchas voice or code modulation.

In operation, it will be observed that switch 23 is first separated fromcontact 26' by generator 24 for a time sufficient for the entirestructure including the conductors of line 1 and antenna 3 to becomecharged to a potential difference V equal to that supplied by battery21. On the next cycle of wave 24a, switch 23 closes with contact 26,forming a conducting circuit path through resistors 22 and 22a. Theeffect is that of putting a second source B in series with the effectivesource A of battery 21, but reversed in polarity relative to thepolarity of source A.

FIGS. 50, 6a, 7a, and 8a show the positive voltage V, contributed by thesource A or battery 21, as a positive constant voltage at successiveintervals in the system cycle. The same set of figures shows theprogress of the negative wave due to the effective source B at the samesuccessive intervals. For example, FIG. 5a shows the situation at theinstant switch 23 is closed; note that the wave due to the effectivesecond source B has not started to flow.

In FIG. 6a, however, the negative wave of voltage V/2 from the effectivesecond source B has begun to flow toward the aperture of antenna 3. Uponreaching the ends of conductors 12 and 12a, of FIG. 4, and upon beingreflected, the situation is depicted in FIG. 7a. It is seen that whenthe V/Z wave reaches the respective ends 8, 8a of antenna conductors 12and 12a, it is reflected and begins to flow'back toward antennajunctions 19, 19a. The total contribution of the efiective source B,beginning at the instant of reversal, is now V volts. It will be seenthat the total potential due to sources A and B between conductors l2and 12a at the aperture 8, 8a of the antenna 3 at the instant ofreversal suddenly drops from +V volts to zero; this instant of time isone of primary interest in the operation of the invention. The wave dueto the effective source B continues to travel back toward junctions 19,19a until the antenna 3, which has served as part of the charging linefor the system, is substantially completely discharged, if the value ofr is the characteristic impedance of line 1. The charging cycle is thenreestablished by the closure of switch 23 and the system may berepeatedly recycled.

It will be readily appreciated that the total potential difference seenacross the aperture 8, 8a of antenna 3, for the same successive instantsof time as described above, may be illustratedas in the respective FIGS.5b, 6b, 7b, and 8b. It is seen that the potential at the antennaaperture due to source A (battery 21) is progressively eaten away by thetravel of the wave due to the effective source B started toward theaperture 8, 811 when switch 23 is closed and then reflected at theaperture ultimately to effect substantial discharge of the line formedby conductors 12 and 12a, the wave having returned to the sourceresistances 22, 221

As noted previously, it is the instant of reflection of the wave fromthe effective source B at the distance L along conductors 12 and 12a,(the aperture of antenna 3) that is of prime interest. Because of thefinite characteristic impedance r of the antenna 3, the leading edge ofthe V/2 wave launched into the aperture or mouth of the antenna, whichis in effect an open circuit, reverses in direction of flow whilemaintaining its previous polarity. Radiation into space of a signalproportional to dV/dt must occur at this instant of time.

N 0 further radiation can obtain until after switch 23 is recycled andconductors 12 and 12a are recharged.

As noted above, if the resistance r of the sum of resistors 22 and 22ais made equal to the characteristic impedance of the transmission linesystem, the reflected wave front terminates in resistors 22, 22a and thepotential difference across the entire line drops to substantially zeroand begins to recharge to approximately rv/R volts. If the value of r isreduced toward zero, the potential across aperture 8, 8a tends toincrease, but the response of the system may be ringing or oscillationfor an extended time. A moderate length of transmission line addedbetween the series circuits 22, 22a, 23, and junctions l9 and 19a may'then be used to delay the instant of time at which radiation occurs.I

FIG. 9 illustrates a form of the invention employing many of the sameelements as used inFIG. 4 and they are therefore identified with similarreference numerals, including transmission line conductors 14, 14a,antenna conductors 12', 12a, battery 21, terminals 19, 19a, mercury reedswitch elements 23, 26, 27, source resistors 22, 22a, and means 25 foractuation of switch blade 23. A moderate length of transmission line hasbeen added between the series circuit 22, 22a, 23 and therespectivejunction points 19, 19a. The added line comprises a firstinner conductor 31 connecting resistor 22 to junction 19, and a secondinner conductor 31a connecting resistor 22a to junction 19a, and anouter tubular conductor 30 surrounding and shielding conductors 31 and31a. For the purpose of ensuring that shielding conductor 30 is at themid-potential between conductors 31, 31a, fixed capacitors 33, 33a areplaced in series across battery 21, being mutually coupled at amid-terminal 36 which is also connected to mid-terminal 37 betweenadjustable trimming capacitors 34 and 34a also placed across battery 21.The mid-terminal 37 is coupled by balanced leads 38, 38a in a balancedmanner to the shield conductor 30. With a 300-volt battery 21, a farfield receiver used with the impulse transmitter of FIG. 9 receives asignal very closely approximately an impulse with a rise time andduration less than 200 picoseconds.

A preferred method of employing the invention is shown in FIG. wherein afurther advantageous arrangement for connecting the mercury reed switchis disclosed. In this apparatus, parts similar to those appearing inFIGS. 4 and 9 bear the same reference numerals. In FIG. 10, actuationmeans 25, which may be a magnetic field supplied by a solenoid (notshown) excited by a pulse generator similar to pulse generator 24 ofFIG. 4 or by a pulse width modulated generator, is adapted to moveswitch blade 123 cyclically between terminals 126 and 127. Blade 123 iscoupled through r/2 resistor 122b to conductor 14. Terminal 127 of theswitch is coupled through r/2 resistor 122 to conductor 14a. Likewise,terminal 126 is coupled through r/2 resistor 122a to conductor 14a.

Referring to FIGS. 10 to 13, switch blade 123 spends the major part ofits operating time in contact either with switch terminal 126 or switchterminal 127 as shown especially in FIG. 11; blade 123 is at terminal126 in the time interval a-b and is at terminal 127 in time intervalc-d, for example. During transit from terminal 126 to terminal 127 (inthe period b-c which is about 100 microseconds in representative-reedswitches), the conductors 12 and 12a of the antenna recharge frombattery 21 through resistors and 20a. When the blade 123 touches switchcontact 126 or switch contact 127, the potential between conductors 14,14a, drops virtually to zero. As in FIG. 12, the line conductors 14,14a, and antenna conductors 12, 12a charge in the interval ending at a,when discharge is brought about substantially instantaneously in a timeon the order of 100 picoseconds. The cycle represented in FIGS. 11 and12 repeats at each switch closure at terminal 126 or 127. As in theapparatus of FIG. 4, the far field signal of the antenna is a functionof the time derivative of 'the collapsing voltage at time a, being seenby the receiver primarily as a series of sharp impulses of briefduration, as in FIG. 13. The sharp pulse series is scarcely modifiedbecause of the slowly varying voltage-change during the-period b-c, forexample. From the foregoing, it is evident that the possibility of ahigher repetition rate is characteristic of the apparatus of FIG. 10.Also, operation at reduced average potentials on conductors 14, 14a ispossible.

It will be apparent to those skilled in the art that the mercury-wettedreed switch, because of its compactness and other advantageousproperties, is a practicalexternally controlled switch for employment inthe invention. Other types of switches may also readily be employed inthe apparatus of FIGS. 4, 9, and 10, such as semiconductor switches ofwell known types whose state of conductivity may be controlled byexternal pulse generators, such as generator 24 of FIG. 4.

Other semiconductor switching arrangements may be employed, includingthe inventive system shown in FIG. 14; in this figure, elements commonto those in FIG. 4 are identified by the same reference numerals,including the balanced r/2 resistors 22 and 22a in series connectionacross conductors 14, 14a, of transmission line 1. Between resistors 22and 22a, are placed series connected transistors 50 and 500, the totalseries circuit including resistor 22, the collector and emitter oftransistor 50, the collector and emitter of transistor 50a, and resistor22a. Between the baseand emitter of transistor 50 is connected aresistor 51; between the base and emitter of transistor 50a is similarlyconnected a resistor 51a. Resistors 22 and 22a are in balancedconfiguration and are selected 'so that when the transistors areconducting, the total resistance in series with transistors 50, 50a isequal to r, the characteristic impedance of line 1 and antenna 3.Resistors 51, 51a serve to provide a direct current path between therespective bases and .emitters of transistors 50, 50a; their resistancevalues must be great enough to permit avalanche operation of transistors50, 50a.

In operation, the circuit of FIG. 14 with the transistors 50, 50anon-conducting permits battery 21 to charge line I and antenna 3, sothat the effective capacitance 52 of the system approaches full charge.Transistors 50, 50a are avalanche mode devices which break down intoavalanche conduction when the voltage between terminals 19, 19a reachesan appropriate value. In practice, one or more suchtransistors may beemployed, depending upon the desired charging level for line 1 andantenna 3. The abrupt discharge of current through transistors 50, 50astarts a voltage wave propagating along conductors 12, 12a toward theaperture 8, 8a of the antenna 3. Upon reversal of the voltage wave atthe aperture 8, 8a, a differentiated impulse is radiated toward the farfield of antenna 3. The voltage wave reflected at the instant ofreversal ultimately drops the potential difference between terminals 19,19a to the point of extinction of current flow through transistors 50,50a. The circuit is then in condition for recharging from battery 21 andautomatically continues to recycle unless the voltage from battery 21 isremoved.

In the foregoing, several embodiments of the invention have beendescribed by means of which impulse radiations may be projecteddirectionally into space. It is seen that the disclosed embodimentsbeneficially employ constant impedance transmission line systemssupporting the non-dispersive TEM mode of energy propagation. It isfurthermore seen that the total transmission line is employed cyclicallyfor the cooperative storage of electrical energy and for its controlledrelease for propagation along the transmission line toward an opencircuited end of the transmission line. Upon reflection of theelectrical energy at the open circuit, directive radiation of an impulsenature occurs instantaneously. In the invention, cooperative use is madeof parts formerly playing only the function of an impulse generatorpart, or only the function of an antenna part. An integrated, compactapparatus is thus provided for the generation and radiation of impulsewaves. It will be clear to those skilled in the art that the naturalstorage capacitance of the transmission line system may be augmented orthat other electrical storage means may be employed. Furthermore, itwill be apparent that other transmission lines propagating thenon-dispersive TEM mode may be employed according to the invention. Itis also clear that no discrete physical transition such as junctions 19,19a need appear in the structure, and that the transmission line systemmay employ a continuous system without a recognizable discontinuitybetween the functional sections of the line.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of the invention in its broader aspects.

What is claimed is:

1. Apparatus for radiating impulses of electromagnetic energycomprising: 7

balanced conductor high frequency transmission line means having asubstantially constant characteristic impedance between first and secondends thereof, current source means adjacent said first end having afirst time constant for uniformly charging said transmission line means,and

switching circuit means having conducting and non-conducting statesadjacent said first end and having when in said conducting state asecond time constant substantially shorter than said first time constantfor causing a field collapsing wave to propagate on said transmissionline means to said second end thereof for partially discharging saidtransmission line means,

said second end of said transmission line means being adapted to reflectsaid field collapsing wave to propagate on said transmission line meanstoward said first end for substantially totally discharging saidtransmission line means into said switching circuit means,

said second end of said transmission line means being further adapted toserve as an antenna aperture for radiating an impulse of electromagneticenergy into space at the instant of reversal of propagation of saidfield collapsing wave.

2. Apparatus as described in claim 1 wherein the impedance of saidswitching circuit means is substantially equal to the characteristicimpedance ofsaid transmission line means.

3. Apparatus as described in claim 1 wherein said balanced conductortransmission line means has first and second planar conductors withopposed major conducting surfaces.

4. Apparatus as described in claim 3 wherein said major conductingsurfaces have a width b and a separation h where the ratio b/h is heldsubstantially constant.

5. Apparatus as described in claim 3 wherein said planar conductors areadapted to propagate traveling electromagnetic waves in the transverseelectromagnetic mode.

6. Apparatus as described in claim 4 wherein said planar conductingsurfaces have a region adjacent said second end in which b progressivelyexpands for the purpose of forming said electromagnetic radiatingantenna aperture.

7. Apparatus as described in claim 3 wherein said first planar conductorhas substantially the shape of a truncated equilateral triangle, thebase of which forms the said second end of said first planar conductor.

8. Apparatus as described in claim 5, wherein said current source meansfor charging said line comprises:

unidirectional potential means, and

first and second resistance means of substantially equal resistance,said potential means being connected through said resistance means tosaid transmission line means.

9. Apparatus as described in claim 5, wherein said switching circuitmeans for discharging said line comprises:

switch means,

first and second resistance means of substantially equal resistance,said switching means being connected through said resistance means tosaid transmission line means.

10. Apparatus as described in claim 9, wherein said substantially equalresistors have a total resistance substantially equal to thecharacteristic impedance of said transmission line means.

11. Apparatus as described in claim 1 wherein said switching circuitmeans comprises first and second substantially equal impedance means andswitch means, said switch means being connected in series relationbetween said first and second impedance means, the total impedance ofsaid switching circuit means being substantially equal to thecharacteristic impedance of said transmission line means.

12. Apparatus as described in claim 1, wherein said switching circuitmeans for discharging said transmission line comprises switch meansadapted to be switched by a pulsed electrical signal.

13. Apparatus as described in claim 1, wherein said switching circuitmeans for discharging said transmission line comprises semiconductorswitch means adapted to initiate discharge when the potential acrosssaid transmission line means reaches a predetermined value.

1. Apparatus for radiating impulses of electromagnetic energy comprising: balanced conductor high frequency transmission line means having a substantially constant characteristic impedance between first and second ends thereof, current source means adjacent said first end having a first time constant for uniformly charging said transmission line means, and switching circuit means having conducting and non-conducting states adjacent said first end and having when in said conducting state a second time constant substantially shorter than said first time constant for causing a field collapsing wave to propagate on said transmission line means to said second end thereof for partially discharging said transmission line means, said second end of said transmission line means being adapted to reflect said field collapsing wave to propagate on said transmission line means toward said first end for substantially totally discharging said transmission line means into said switching circuit means, said second end of said transmission line means being further adapted to serve as an antenna aperture for radiating an impulse of electromagnetic energy into space at the instant of reversal of propagation of said field collapsing wave.
 2. Apparatus as described in claim 1 wherein the impedance of said switching circuit means is substantially equal to the characteristic impedance of said transmission line means.
 3. Apparatus as described in claim 1 wherein said balanced conductor transmission line means has first and second planar conductors with opposed major conducting surfaces.
 4. Apparatus as described in claim 3 wherein said major conducting surfaces have a width b and a separation h where the ratio b/h is held substantially constant.
 5. Apparatus as described in claim 3 wherein said planar conductors are adapted to propagate traveling electromagnetic waves in the transverse electromagnetic mode.
 6. Apparatus as described in claim 4 wherein said planar conducting surfaces have a region adjacent said second end in which b progressively expands for the purpose of forming said electromagnetic radiating antenna aperture.
 7. Apparatus as described in claim 3 wherein said first planar conductor has substantially the shape of a truncated equilateral triangle, the base of which forms the said second end of said first planar conductor.
 8. Apparatus as described in claim 5, wherein said current source means for charging said line comprises: unidirectional potential means, and first and second resistance means of substantially equal resistance, said potential means being connected through said resistance means to said transmission line means.
 9. Apparatus as described in claim 5, wherein said switching circuit means for discharging said line comprises: switch means, first and second resistance means of substantially equal resistance, said switching means being connected through said resistance means to said transmission line means.
 10. Apparatus as described in claim 9, wherein said substantially equal resistors have a total resistance substantially equal to the characteristic impedance of said transmission line means.
 11. Apparatus as described in claim 1 wherein said switching circuit means comprises first and second substantially equal impedance means and switch means, said switch means being connected in series relation between said first and second impedance means, the total impedancE of said switching circuit means being substantially equal to the characteristic impedance of said transmission line means.
 12. Apparatus as described in claim 1, wherein said switching circuit means for discharging said transmission line comprises switch means adapted to be switched by a pulsed electrical signal.
 13. Apparatus as described in claim 1, wherein said switching circuit means for discharging said transmission line comprises semiconductor switch means adapted to initiate discharge when the potential across said transmission line means reaches a predetermined value. 